A gasoline or petrol spark ignited engine may include direct fuel injection. Fuel may be directly injected into an engine cylinder so that evaporation of the injected fuel may cool a charge in the engine cylinder. By cooling the cylinder charge, the engine may be operated at higher loads before engine knock occurs as compared to a port fuel injected engine. As such, the engine may operate more efficiently and may provide more power than a port fuel injected engine. However, directly injecting fuel into a cylinder may also provide an opportunity for injected fuel to stratify within an engine cylinder leading to carbonaceous exhaust. The carbonaceous exhaust may be stored in a particulate filter where it may be subsequently oxidized so that less particulate matter may be exhausted to atmosphere. Over time, the particulate filter may fill with carbonaceous soot such that the particulate filter may need to be regenerated. One way to determine whether or not the particulate filter is storing more than a threshold amount of carbonaceous soot is to measure a pressure change or pressure differential across the particulate filter. If the particulate filter is loaded with carbonaceous soot, a higher pressure differential may be indicated when engine air flow is high. However, it may be possible for a hose of a differential pressure sensor to detach from its anchored position due to maintenance or unforeseen circumstance. If the differential pressure sensor's hose becomes detached, it may be difficult to determine whether or not the differential pressure sensor is providing reliable information. Therefore, it may be desirable to provide a way of ascertaining whether or not differential pressure sensor data is reliable.
The inventor herein has recognized the above-mentioned issue and has developed a vehicle operating method, comprising: in response to an exhaust system sensor diagnostic request, rotating an engine in a reverse direction without fueling the engine; receiving data from a differential pressure sensor to a controller while rotating the engine in the reverse direction; and adjusting engine operation via the controller in response to the data from the differential pressure sensor.
By rotating an engine in reverse when the engine is not combusting air and fuel, it may be possible to provide the technical result of greater flow through an engine than if the engine were rotating in a forward direction when the engine is not combusting air and fuel so that a signal to noise ratio of exhaust sensor output may be improved. Further, by rotating the engine without combustion, an exhaust sensor diagnostic may be performed when there are no vehicle occupants so that the diagnostic may be less detectable. Further still, exhaust sensor diagnostics may be selectively performed during engine operation at times when they may be less likely to be detected.
The present description may provide several advantages. For example, the approach may allow for improved sensor diagnostics. In addition, the approach may provide diagnostics while the engine is operating or not operating so that an exhaust sensor may be diagnosed in a timely manner. Additionally, the approach may provide an improved signal to noise ratio for exhaust sensor output.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.